This invention relates to a structure of a wiring board used for contacting or connecting with a given electronic part such as an IC or the like, and more particularly to a conductive bump in a wiring board to be subjected to the above contact or connection.
In this embodiment, the term xe2x80x9ccontactxe2x80x9d refers to an electrical connection through a free contact surface which comes into and out of connection freely, and the term xe2x80x9cconnectionxe2x80x9d refers to an electrical connection disconnectably joined by solder or the like.
Conventionally, when a given electronic part such as an IC is loaded on a wiring board for electrical connection, a wiring pattern is formed on the surface of the wiring board and an unlike metal such as a conductive paste or the like is bulged to form a conductive bump on the surface of a lead forming this wiring pattern, so that a terminal of the electrical part is contacted with or connected to the conductive bump.
Also, for achieving an electrical connection between a wiring board and another wiring board, according to another conventional method, a conductive bump is formed on a lead forming the wiring pattern of one of the wiring boards and contacted with or connected to a terminal formed on an end of a lead of the other wiring board.
However, the above conventional method for forming the conductive bump on the conductive lead of the wiring board by raising an unlike metal such as a solder paste or the like, has problems, such that the method for forming the conductive bump is complicated, positional accuracy is difficult to obtain, configuration of the height of the conductive bumps is irregular, and so forth. Although this conventional technique can effectively cope with the requirement of a smaller pitch arrangement of terminals, actual practice of the conventional technique is jeopardized because of the above problems.
The present invention has been accomplished to overcome the above problems.
It is, therefore, a general object of the present invention to provide a structure of a conductive bump in a wiring board which is capable of properly solving the above problems and enhancing the actual practice thereof.
To achieve the above object, there is essentially provided a structure of a conductive bump in a wiring board having a wiring pattern on a surface of an insulating base, characterized in that a local portion of the insulating base is raised from the surface of the insulating base to form a projection and a surface of the projection is covered with a part of a lead forming the wiring pattern to form the conductive bump.
From another aspect of the present invention, there is also provided a structure of a conductive bump in a wiring board characterized in that a bump is formed by a part of a lead forming the wiring pattern and a cavity is formed in the bump.
A more complete description of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.